She paid tribute to her "wider legacy" and her ability "not only to touch
people's lives but to change them".

Culture Secretary Tessa Jowell accompanied the Queen for a closer inspection of the 700-tonne memorial.

And the 200 people who travelled from across the UK were rewarded when the royals did a "walkabout" and met many of those who made the journey.

Angela Bentham, 38, from Goldthorpe, South Yorkshire, said the Queen told her: "It's nice to see people coming in
to support Diana."

The design consists of a large Cornish granite ring with water pouring on to it, flowing in two directions at different speeds, and is supposed to sit "like a necklace" around the contours of the site.

FOUNTAIN FACTS

Work begins June 2003

Opened on schedule July 2004

Cost - £3.6m

Size - 80m x 50m

545 stones of De Lank granite from a Cornish quarry, cut in the Mountains of Mourne, Co Down.

The Princess Diana Memorial Fountain Committee, led by the princess's friend Rosa Monckton, finally picked two competing designs from an initial 10,000 in 2002.

After a vote, Gustafson's design was selected over a reportedly more avant-garde proposal by Bombay-born British artist Anish Kapoor.

'Inclusive'

Diana's late mother Frances Shand Kydd criticised the chosen memorial as having a "lack of grandeur".

But Ms Gustafson said she wanted the fountain, built to the south of the Serpentine, to be accessible and to reflect Diana's "inclusive" personality.

Ms Gustafson told BBC News Online: "Above all I hope that it provides a fitting memorial for the princess and does credit to the amazing person that she was."

William Weston, chief executive of the Royal Parks, described the fountain as "a contemporary structure in a classical landscape".

DIANA, PRINCESS OF WALES MEMORIAL FOUNTAIN

1 Water enters fountain at highest point, pumped at 100 litres/second.2 Water travelling east bounces down steps.3 A specially sculpted channel makes the water rock gently.4 Water picks up momentum and is invigorated by jets.5 Water flowing westwards resembles a babbling brook.6 Air bubbles are introduced as it approaches a waterfall before entering a water feature created by its flow over carved stone.7 Final destination is the reflecting pool, where water from east and west meet before being pumped out to restart cycle.